[Not Applicable]
1. Field of the Invention
The present invention relates to a golf club head. More specifically, the present invention relates to a face section of a golf club head to reduce energy losses when impacting a golf ball.
2. Description of the Related Art
Technical innovation in the material, construction and performance of golf clubs has resulted in a variety of new products. The advent of metals as a structural material has largely replaced natural wood for wood-type golf club heads, and is but one example of this technical innovation resulting in a major change in the golf industry. In conjunction with such major changes are smaller scale refinements to likewise achieve dramatic results in golf club performance. For example, the metals comprising the structural elements of a golf club head have distinct requirements according to location in the golf club head. A sole or bottom section of the golf club head should be capable of withstanding high frictional forces for contacting the ground. A crown or top section should be lightweight to maintain a low center of gravity. A front or face of the golf club head should exhibit high strength and durability to withstand repeated impact with a golf ball. While various metals and composites are known for use in the face, several problems arise from the use of existing materials.
Existing golf club face materials such as stainless steel exhibit desired high strength and durability but incur large energy losses during impact with the golf ball as a result of large ball deformations. An improvement in impact energy conservation, in conjunction with proper golf ball launch parameters, is a design goal for golf club manufacturers. The problem still exists of identifying a combination of material properties exhibiting improvements in conservation of impact energy during impact with the golf ball.
When a golf club head strikes a golf ball, large impact forces are produced that load a face section, also called a striking plate, of the golf club head. Most of the energy is transferred from the golf club head to the golf ball; however, some energy is lost as a result of the impact. The present invention comprises a golf club striking plate material and geometry having a unique combination of material properties for improved energy efficiency during impact with the golf ball.
The golf ball is typically a core-shell arrangement composed of polymer cover materials, such as ionomers, surrounding a rubber-like core. The golf ball materials have stiffness properties defined as the storage and loss moduli for compression (Exe2x80x2ball,Exe2x80x3ball) and storage and loss moduli for shear (Gxe2x80x2ball,Gxe2x80x3ball) that are strain (or load), strain rate (or time rate of loading), input frequency, and temperature dependent. The compression loss factor (xcex7E) and shear loss factor (xcex7G) (damping or energy loss mechanisms), which are defined as the ratio of loss modulus to the storage modulus, are also strain, strain rate, input frequency, and temperature dependent. The golf ball loss factors, or damping level, is on the order of 10-100 times larger than the damping level of a metallic golf club striking plate. Thus, during impact most of the energy is lost as a result of the large deformations, typically 0.05 to 0.50 inches, and deformation rates of the golf ball as opposed to the small deformations of the metallic striking plate of the golf club head, typically 0.025 to 0.050 inches.
By allowing the golf club head to flex and xe2x80x9ccradlexe2x80x9d the golf ball during impact, the contact region as well as contact time between the golf ball and the striking plate of the golf club head are increased, thus reducing the magnitude of the internal golf ball stresses as well as the rate of the stress build-up. This results in smaller golf ball deformations and lowers deformation rates, both of which produce much lower energy losses in the golf ball during impact. The static flexibility is inversely proportional to the striking plate stiffness, while the dynamic flexibility is inversely proportional to square of the striking plate bending natural frequency. In other words, a decrease in plate stiffness will cause the static flexibility to increase, while doubling the plate bending natural frequency will reduce dynamic flexibility to a level xc2xc of the original striking plate. Increasing the static or dynamic flexibility can be accomplished via several different configurations for the golf club head: altering geometry of the face section; altering attachment of the striking plate to the club-head body; reducing the thickness of the striking plate; or through the innovative use of new structural materials having reduced material stiffness and/or increased material density. Material strength of the striking plate of the golf club head in conjunction with impact load from contact with the golf ball determines the minimum required thickness for the face section. The greater the available material strength, the thinner the striking plate can be, and thus greater the flexibility. So the material properties that control static and dynamic flexibility are decreased compression stiffness, increased density, and increased strength. The present invention specifies which face materials and static/dynamic flexibilities provide improved energy conservation during impact of the golf club head and the golf ball. Materials used in the face section of the golf club head constitute an additional important factor in determining performance characteristics of coefficient of restitution (COR), launch angle, spin rate and durability.
One object of the present invention is to improve impact efficiency between a golf club head and the golf ball.
Another object is to designate a range of material properties to increase the static flexibility, otherwise described as reduced bending stiffness, of the striking plate of the golf club head. Any number of materials having requisite limitations of stiffness and strength can be utilized in the manufacture of the golf club of the present invention to produce a compliant, or softer flexing performance during impact with the golf ball.
Another object is to designate a range of material properties to increase the dynamic flexibility, otherwise described as reduced bending natural frequency, of the striking plate of the golf club head. Any number of materials having requisite limitations of stiffness and strength can be utilized in the manufacture of the golf club of the present invention to produce a compliant, or softer flexing performance during impact with the golf ball.
A further object of the present invention is a wood-type golf club head having a face section of a first material and a body section of a second material.
Another object of the present invention is a wood-type golf club head having a face section of a metal material.
Another object of the present invention is a wood-type golf club head having a face section of a non-metal material.